Re: [Qemu-devel] [PATCH v2 7/7] intel-iommu: keep buggy EIM enabled in 2.7 machine type

[Peter Xu]

On Thu, Sep 29, 2016 at 01:23:29PM +0200, Radim Krčmář wrote:

[...]

> @@ -2481,11 +2482,14 @@ static void vtd_realize(DeviceState *dev, Error 
> **errp)
>      if (s->intr_eim == ON_OFF_AUTO_AUTO && !x86_iommu->intr_supported) {
>          s->intr_eim = ON_OFF_AUTO_OFF;
>      }
> +    if (s->intr_eim == ON_OFF_AUTO_AUTO && pcmc->buggy_intel_iommu_eim) {
> +        s->intr_eim = ON_OFF_AUTO_ON;
> +    }
>      if (s->intr_eim == ON_OFF_AUTO_AUTO) {
>          s->intr_eim = kvm_irqchip_in_kernel() ? ON_OFF_AUTO_ON
>                                                : ON_OFF_AUTO_OFF;
>      }
> -    if (s->intr_eim == ON_OFF_AUTO_ON) {
> +    if (s->intr_eim == ON_OFF_AUTO_ON && !pcmc->buggy_intel_iommu_eim) {
>          if (kvm_irqchip_in_kernel() && !kvm_enable_x2apic()) {
>              error_report("intel-iommu,eim=on requires support on the KVM 
> side "
>                           "(X2APIC_API, first shipped in v4.7).");

No matter how we would treat this patch, I see that we are stacking up
if clauses here. So IMHO maybe it's time to award EIM a new routine:

  int vtd_eim_detect(IntelIOMMUState *, Error **errp);

And squash all these conditions in. Then in vtd_realize():

  if (vtd_eim_detect(s, errp)) {
      return;
  }

Thanks,

-- peterx